This invention relates to a method and device for press-forming a hollow article having a flange in one step by utilizing a method of forming materials by plastic deformation.
There is a great variety of hollow articles having flanges at their ends, such as synchronizer rings c (having through hole) as shown in FIG. 1. A conventional method for producing these articles is shown in FIGS. 2(I)-2(IV).
In FIGS. 2(I) through 2(IV), there are indicated steps of conventional production of a synchronizer ring gear c, such as shown in FIG. 1 wherein a material blank j obtained by forging and the like process is subjected to coining on a bevelled and indented surface k thereof, a tooth pattern 1 being thereafter press-formed, and the waste part m is punched off. In addition, the internal hole n and the boss part o must be machined, so that the entire process of the production requiring considerable labor, and, furthermore, the productivity thereof has been extremely low.